1. Field
The present disclosure relates generally to light beam scanners and light beam scanning assemblies and elements, and more particularly, methods of manufacturing, tuning and adjusting the same.
2. Brief Description of the State of Knowledge in the Art
In laser-based barcode scanning equipment, and particularly in portable laser-based barcode scanning equipment, a scan component is used to dither a mirror. The moving mirror is used to sweep a laser beam across a barcode target to be read. This scan component is often called a laser scanning assembly. A laser scanning assembly is a critical component in portable laser-based barcode readers. Desirable attributes for a laser scanning assembly are small size, ruggedness, energy efficiency, freedom from beam shifting when held in different orientations, and immunity to unwanted motions of the scan beam when held by an operator.
In general, the performance of a laser a barcode scanner is defined by a number of factors including: the accuracy and performance of its scanning element; the dynamic characteristics of the scanning element; the size and mass of the scanning element; manufacturability; and energy efficiency.
Conventional flexural element-based laser scanning assemblies are formed from cantilevered beams of plastic film or other flexible materials and are not balanced structures. Several such laser scanning assemblies are described in U.S. Pat. No. 6,173,895 to Plesko, which suffer from unwanted tilting or drooping of the scan mirror when held in different orientations due to the effects of gravity, especially if the scan mirror and moving magnet are large. Further, flexible film flexural elements can become permanently distorted if the device is dropped or otherwise exposed to rough handling. Such distortion produces shifted scan lines or scan lines that are no longer straight.
Shaft-based laser scanning assemblies, such as described in U.S. Pat. No. 7,420,721 B2 to Takeuchi, are also prone to the wobble of the scan mirror induced by gravity or operator movement when used in portable hand held applications. The above-described drawbacks are exacerbated by the use of large scan mirrors required for long range scanning
Beam shifting may also be caused by the addition of an inductive pole piece within the electromagnetic drive coil, (see, e.g., U.S. Pat. No. 7,420,721 B2). The pole piece generates a magnetic bias that can tilt the scan mirror or cause unwanted forces, which result in undesirable speed perturbations of the scan line. Thus, tedious adjustment is needed to ensure proper operation of the laser scanning assembly, and may be subject to error.
Further drawbacks associated with conventional laser scanning assemblies are radical bursts of acceleration and deceleration of the scan mirror, which distort the timing of light signals reflected from a barcode target. Distortion often occurs when a pulse of current, such as a short duty cycle square wave, is used as a drive waveform, especially at non-resonant frequencies.
Thus, there is a great need in the art for a new and improved laser scanning assembly that can be used in diverse scanning applications, without the shortcomings and drawbacks of prior scanning apparatus and methodologies.